Preparation And Properties Of Modified Calcium Carbonate Compounded Bagasse Cellulose Superabsorbent

Natural polymer-based superabsorbent resin（SAR）is widely used in agriculture,construction,industry and other industries due to its high water absorbency,however,the current commercial SAR still has the defects of poor salt resistance,slow water absorption rate,low gel strength after water absorption,and non-degradation.Therefore,it is of great significance to develop degradable SAR with salt resistance,high gel strength after water absorption,good liquid absorption speed.Bagasse is the residue of sugarcane juice crushing or sugar making,which contains a lot of cellulose,and it is cheap and easy to degrade,and it can be chemically modified to prepare degradable SAR.Ca CO₃is an inexpensive and widespread inorganic material,and its modification and addition to bagasse cellulose-based SAR can improve its salt tolerance and gel strength after water absorption.In this paper,nano-Ca CO₃was first prepared by solid-phase reaction,and then nano-Ca CO₃was modified with silane coupling agent to obtain modified nano-Ca CO₃（MNC）.Then bagasse was used as raw material,acrylamide（AM）and acrylic acid（AA）were grafted monomers,and MNC was used as inorganic additives,the bagasse cellulose composite modified nano-Ca CO₃superabsorbent（CAAMC）with double cross-linked network was prepared by the aqueous solution method.Afterwards,the semi-interpenetrating network structure CAAMC/PVA superabsorbent was prepared with CAAMC as the first cross-linked network composite PVA.The main research contents are as follows:（1）First,nano-Ca CO₃was prepared by solid-phase reaction,then the nano-Ca CO₃was modified by 3-aminopropyltrimethoxysilane（KH550）to prepare modified nano-Ca CO₃（MNC）.Fourier transform infrared spectroscopy（FT-IR）and X-ray photoelectron spectroscopy（XPS）analysis showed that nano-Ca CO₃was bound to 3-aminopropyltrimethoxysilane through Ca-O-Si.Scanning electron microscope（SEM）results showed that the nano-Ca CO₃before and after modification were all granular,and the particle size was about50 nm.Since the chemically modified MNC surface is rich in organic groups,the dispersionof nano-Ca CO₃particles in the composite superabsorbent resin can be improved and the interface defects between the organic-inorganic composite materials can be reduced.（2）Bagasse as raw material,MNC prepared in Chapter 2 as inorganic additive component,bagasse-cellulose composite modified nano-Ca CO₃superabsorbent resin（CAAMC）was preparation by aqueous solution polymerization.The results of FT-IR and XPS analysis indicated that modified nano-Ca CO₃（MNC）was combined with AA and AM through the chemical bond C-N.SEM results show that the network structure of CAAMC can be effectively adjusted by changing the content of MNC,therefore,the water absorption properties of CAAMC are affected.MNC plays the dual role of crosslinking and filler.The maximum water absorbency of CAAMC reaches 712 g/g in deionized water and 72 g/g in 0.9 wt%Na Cl solution,MNC effectively improved the salt tolerance of CAAMC.（3）In order to improve the water absorption rate of SAR,the CAAMC prepared in Chapter 3 was used as the first cross-linked network,and then PVA was composited with CAAMC to prepare a fast water absorbent CAAMC/PVA with a semi-interpenetrating network structure.The effects of PVA on the water absorption rate of CAAMC/PVA were studied,and the results showed that the network structure of CAAMC/PVA can be changed by changing the addition time and amount of PVA,thereby affecting the liquid absorption rate.FT-IR and solid state ¹³C-NMR analysis showed that CAAMC and PVA were combined through hydrogen bonding,combined with SEM analysis results showed that CAAMC/PVA had a multi-layer structure,indicated that CAAMC/PVA had a semi-interpenetrating network.structure.CAAMC/PVA can absorb 290 g/g deionized water,47 g/g 0.9wt%Na Cl solution,42 g/g artificial blood and 27g/g artificial urine within 1 minute,it is also higher than that of superabsorbent resins in some commercial diapers.（4）To find out mechanism of the structural changes of SAR during the entire water-swelling process process,and the effect of different functional groups,we used Materials Studio to simulate the structural changes of the cellulose branches grafted with amino and carboxyl groups during water absorption,and calculated the adsorption energies of amino groups carboxyl groups and hydroxyl groups contained in PVA for water molecules,and the adsorption energies of co-adsorption of water molecules between different functional groups.The simulation results show that the carboxyl group plays an important role in increasing the volume of the resin after absorbing water.When the carboxyl group and the hydroxyl group of PVA jointly absorb water molecules,the adsorption of water molecules has a synergistic effect...